Interpretive Summary: The USDA-ARS Western Regional Plant Introduction Station (WRPIS), Pullman WA, maintains more than 15,000 accessions of forage and turf grass species. Original seed samples received are usually of low quantity, so most must be grown-out or regenerated to provide genetic material for distribution to the scientific community. Various studies have been conducted to ensure that the genetic composition of accessions were maintained as close to the original as possible. In field research, sample of annual ryegrass with an equal number of seeds per plant from field plots were found to be best for maintaining allelic frequencies. But genetic diversity (heterozygosity and allelic richness) was maintained nearly as well with other sampling methods that were far less costly to produce. Bromegrass marker plots integrated into WRPIS seed-regeneration nurseries at two locations resulted in average contamination of 4.2% at distances between 22 and 27 m. Thus a relatively low level of pollen contamination appear possible in bulk samples and with modest isolation distances. Significant progress has been make in the management of regeneration nurseries at the WRPIS to ensure that the genetic integrity of accessions is maintained.

Technical Abstract:
Germplasm managers at the Western Regional Plant Introduction Station (WRPIS) have focused on improving seed regeneration in forage and turfgrass species through studies of diversity maintenance, using isozyme markers in annual ryegrass (Lolium multiflorum Lam.) and through studies of pollen isolation, using strains of dominant and recessive glabrous smooth bromegrass (Bromus inermis Leyss.). Balanced samples of annual ryegrass (an equal number of seeds per plant) from field plots were best for maintaining allelic frequencies, but genetic diversity (heterozygosity and allelic richness) was maintained nearly as well in bulk samples (seeds proportionally assembled according to seeds per plant) during early regeneration cycles. In 1995, bromegrass marker plots integrated into WRPIS seed-regeneration nurseries at two locations resulted in average contamination of 4.2% at distances between 22 and 27 m. Diversity maintenance in early regeneration cycles and a relatively low level of pollen contamination appear possible in bulk samples and with modest isolation distances.